This invention relates to the manufacture of tubes for filter cigarettes - that is, empty tubes of cigarette paper closed at one end by a plug of tobacco smoke filtering material. The tubes are intended to be retailed in this empty condition, to be filled with tobacco by the customer; hand operated machines for the latter purpose are commercially available.
In the method and apparatus according to the invention individual plugs are continuously supplied, longitudinally spaced apart, onto a continuously advancing band or tape of cigarette paper which carries the plugs continuously through a wrapping garniture in which the paper is wrapped around the plugs to yield continuously a tube of the cigarette paper (usually with a lapped and stuck longitudinal seam) having the plugs spaced therealong at the required intervals. The continuously produced tube is cut transversely as it is formed into individual lengths each closed by a filter plug at one end and opens at the other for the subsesquent receipt of tobacco. The length ratio of empty tube to filter plug in the product tubes might for examples be 3 or 4 to 1, or higher.
The production of tubes having such a high length ratio can in practice pose registration difficulties. Unless the individual plugs are initially spaced accurately and uniformly along the cigarette paper the final cutting step can lead to an unacceptable proportion of useless product tubes--e.g., tubes having plugs of the wrong length or plug portions at each or neither end. Usually the initially supplied filter plugs are double length plugs and are spaced apart by double the length of the empty tube portion in the individual product tubes; the continuously produced tube is then cut midway along each plug and midway between them.